1. Field of the Invention
The present invention relates to an image reading apparatus (e.g., a scanner, a copier, and a facsimile) that includes a multifeed (MF) detecting function including an ultrasonic (US) sensor, and a multifeed determining method and a multifeed determining program for determining a multifeed based on the result of detection by the multifeed detecting function.
2. Description of the Related Art
In an image reading apparatus (image scanner apparatus), there is widely used an MF detecting function using an US sensor that can detect paper overlapping (e.g., Japanese Patent Application Laid-open No. 2004-269241). However, there is a case where the MF detecting function erroneously detects a medium such as a seal purposely attached to the paper as a multifeed.
As means for avoiding this case, United States Patent Application No. 2005/0228535 discloses a technology for previously setting a length with which multifeed detection is disabled through a panel on a scanner before reading is started, and user manual (functional detail) of scanner “DR-X10C” released in home page of cannon inc. “http://cweb.canon.jp/manual/dr/pdf/drx10c-usermanual2.pdf” discloses a technology for previously setting a starting position and an ending position at which multifeed detection is disabled through a screen on a personal computer connected to a scanner before reading is started.
However, according to the conventional technologies, there is a problem that the length and the position to be disabled have to be previously set, and this causes an operator to carry out complicated and troublesome operations for the setting.